A plate mill is a type of machine tool that is used to machine large flat workpieces having a substantial length and width, but relatively little height. Because the workpiece is large, the plate mill itself is relatively large, and in large machines, rigidity and the ability to resist deformation during operation are important design considerations. It is also important in high performance machines that the rigidity of the machine remain as constant as possible throughout the working range of the machine. This allows for optimal process parameters to be utilized throughout the envelope of machine operation instead of having to vary the process parameters depending on the location of the working tool in the workzone.